Various types of accelerators are commonly used in industrial applications for advancing a workpiece toward or away from an operating station. For example, in connection with tube severing operations in which successive sections of a length of tubing are cut to a desired size, the tubing is axially fed toward a tube cutoff machine which typically includes a pressoperated cutting unit. The cutting unit includes a pair of jaws which grip the tube and a knife which severs the clamped tubing. A mechanical accelerator is normally provided to feed the tubing toward the dieset.
Prior art tube feeding accelerator mechanisms consist of a number of movable mechanical parts, such as mechanically driven rollers which engage the sides of the tubing however, this approach is undesirable for several reasons. Jamming sometimes occurs when the feed-end of the tubing engages the face of the rollers at an angle which is too severe. Also, it is not uncommon for the rollers to impart skid marks or mars on the tubing. Perhaps more importantly, these previous mechanisms are relatively complex, and therefore costly in their construction and require periodic replacement of various component parts, such as the tube engaging rollers, which are subject to rapid wear.
Another problem associated with prior art accelerator systems, and particularly those employing tube-engaging rollers is that of poor repeatability of cutting length. Normally, prior art systems employ a mechanical stop for engaging the end of the tubing after the desired length thereof has been fed through the cutoff station. If the rollers are disengaged from the tubing prematurely, the end of the tubing does not reach the stop, in which case the severed section is too short. On the other hand, if the tubing is fed too quickly it sometimes rebounds after engaging the stop thus also resulting in a severed length which is too short.
From the foregoing, it is apparent that there is a clear need in the art for a linear accelerator system for use with a cutoff apparatus which eliminates each of the problems discussed above.
Accordingly, it is a primary object of the invention to provide a linear accelerator system which avoids the use of moving parts for feeding the tubing, including the need for tube-engaging rollers or the like.
Another important object of the invention to provide an accelerator system of the type described above which is readily adaptable for feeding tubing of differing diameters.
A still further object of the invention is to provide an accelerator system as described above which includes a gaging system that eliminates rebounding of the tubing from a gage stop, thereby to provide highly repeatable cutting length accuracy.
Another object of the invention is to provide an accelerator system as described above which operates to brake the tubing to the proper length without the need for a gage stop.
These, and further objects of the invention will be made clear, or will become apparent from a description of the preferred embodiment described hereinafter.